46 CFR § 154.447 - Allowable stress.

(a) An independent tank type B designed from bodies of revolution must have allowable stresses 3 determined by the following formulae:

3 See Appendix B for stress analyses definitions.

σm≤f

σL≤1.5 f

σb≤1.5 F

σL + σb≤1.5 F

σm + σb≤1.5 F

where:

σm = equivalent primary general membrane stress 4

4 See Appendix A for equivalent stress.

σL = equivalent primary local membrane stress 4

σb = equivalent primary bending stress 4

f = the lesser of (σB/A) or (σY/B)

F = the lesser of (σB/C) or (σY/D)

A, B, C, and D = stress factors in Table 2.

Table 2—Values for Stress Factors

	Nickel steel and carbon manganese steel values	Austenitic steel values	Aluminum alloy values
Stress factors:
A	4.0	4.0	4.0
B	2.0	1.6	1.5
C	3.0	3.0	3.0
D	1.5	1.5	1.5

(b) An independent tank type B designed from plane surfaces must have allowable stresses specially approved by the Commandant (CG-ENG).

[CGD 74-289, 44 FR 26009, May 3, 1979, as amended by CGD 82-063b, 48 FR 4782, Feb. 3, 1983]